In the systems for burning liquid fuel in combustion chambers, there are known systems which feed liquid fuel to the combustion chambers and systems which vaporize liquid fuel in advance and feed gaseous fuel to the combustion chambers. As systems which feed fuel to the combustion chambers of internal combustion engines, there are known systems which inject liquid fuel to the engine intake passage or combustion chambers and systems which vaporize liquid fuel at an evaporator, then inject it to the engine intake passage or combustion chambers. As systems which vaporize the liquid fuel at an evaporator and feed it to combustion chambers, for example, there is known a system of using liquefied petroleum gas (LPG) or another gaseous fuel.
Japanese Patent Publication No. 9-4528 A1 discloses an internal combustion engine which evaporates and vaporizes liquid fuel in a warmup operation, then feeds the vaporized fuel to the engine intake passage. This publication discloses to evaporate the fuel at the relatively low temperature in the warmup operation after startup of the internal combustion engine. It discloses that the fuel vapor which is produced at the fuel evaporator in the warmup operation only contains highly volatile fuel constituents and remarkably reduces the amount of release of hydrocarbons which are contained in exhaust gas.
This publication discloses to control the feed of fuel to the fuel evaporator in accordance with the engine operation at the time of a warmup operation by a fuel adjusting system. Further, it discloses that the heating output of the fuel evaporator is related to the amount of feed of fuel and is advantageously controlled proportionally to the fuel feed amount. Further, it discloses to feed the fuel to the combustion chambers after the completion of the warmup operation by injecting liquid fuel from a fuel injector to the inside of the intake pipe.